One of the major issues in physics nowadays is how to extend the Standard Model (SM) such that successfully accounts for some missing pieces (neutrinos [1]}, strong CP [2]}, among others) and also provides a solid dark matter candidate. From the particle physics point of view, effective field theories have been proposed in which one or more particles - scalars, vectors and/or fermions - from a hidden sector could emerge, potentially coupling to the visible sector through “portals", interaction terms that open a channel between visible and hidden sectors that could leave imprints on relevant observables. Such particles could then provide a stable candidate for dark matter.
